Part of our NPR Ed series on why people play and how play relates to learning.

The game of marbles might seem simple, but behind it is an extensive vocabulary.

"After you're in it for a little while, it kind of becomes second nature to you," says Doug Watson. He's what he calls a free-agent coach, and a marble collector who specializes in early American machine-made marbles and handmade German marbles.

The trade lingo for marbles players — mibsters, some call themselves — bears some similarities to other games and even other worlds entirely like cars, Watson explains.

"Dubs might mean something completely different [for] somebody else. It might mean rims on a car. But in marbles, that's when you take one shot and you knock two out on one shot," he explains.

Then there's lagging, a term you might be familiar with if you're a pool player.

"I know pool shooters will 'lag' to determine the first shot. Same thing in marbles," Watson said.

When NPR's Claudio Sanchez and Sami Yenigun traveled to Wildwood, N.J., for the National Marbles Tournament, they dove right into the game, and the vernacular that comes along with it.

So, if you're a wannabe mibster, or maybe even just someone with a passing interest, here's our shot at demystifying the language of marbles:

Aggies(n.) — A marble made out of agate or that appears to be made out of agate.